In research and development laboratories, among other types of facilities, there are applications that require moving an element (e.g., test strips, a microtitre plate, etc.) a precise distance to a desired location to perform a function at that location. Typically, such movement must be accomplished in a repetitive manner at a precise time interval. Such a task can be performed by an incremental positioner/motion controller.
Sophisticated or "intelligent" motion controllers are often used for such service. Motion controller 100, depicted in FIG. 1, is typical of such intelligent controllers.
Intelligent motion controller 100 includes a control unit 102 and a motorized stage 110. Control unit 102 includes control means 104, depicted figuratively as a collection of switches and rheostats that control a variety of parameters related to stage movement. Control means 104 may control, for example, the direction of stage motion (e.g., forward or reverse), stage speed, coarse or fine stage movement, and the acceleration and deceleration of every movement. Hence the designation "intelligent."
A first cable 106 provides electrical connection between control unit 102 and motorized stage 110, and a second cable 108 attaches to a power supply. Motorized stage 110, which is depicted as a linear stage, includes a motor 112 that is operatively connected to a stage 114.
While such intelligent motion controllers are usually capable of positioning a stage to a high degree of resolution (i.e., about 1 micron accuracy for linear positioners and about 0.004.degree. for rotary positioners), and are quite flexible within the parameters of their operation, they do suffer from several significant shortcomings. In particular, such motion controllers are relatively slow and they are rather expensive. Regarding cost, a motion controller having the capabilities of intelligent motion controller 100 may sell for over $2000 (at least about $800 for the control unit and about $1,200.00 for the motorized stage). Moreover, in view of the complexity of such devices, reliability may be an issue as well.
There may be some applications in which the flexibility offered by such an intelligent controller justifies its cost. There will, however, be many other applications in which process parameters remain fixed (e.g., the positional increment is fixed) so that it may be difficult to cost-justify such an intelligent motion controller. Also, high-speed positioning may be required, which may be beyond the capabilities of the aforedescribed intelligent controllers. Or, a smaller and less expensive system may be desired.
As such, the art would benefit from a fast, inexpensive and reliable incremental positioner.